The invention relates to a method for treating the liquid phase of contaminated materials, especially infected materials, which are fed in a treatment chamber to a high-temperature disinfecting apparatus, heated and disinfected or sterilized, and removed to a discharge, a defined collecting area for liquid being provided at the input end of the transport system in the treatment chamber.
The invention furthermore relates to an apparatus for treating contaminated materials, especially infected materials, in which the latter are delivered through an input unit to a transport system running in a treatment chamber, and heated and disinfected or sterilized, and are removed to a discharge, a defined area for collecting liquid being provided at the input end of the transport system in the treatment chamber.
In DE 197 17 839 a high-temperature disinfecting or sterilization apparatus has been described, which is suited especially for wastes specific to hospitals and in which the wastes are fed through in inlet hopper and a shredder to two screw conveyor sections arranged in tandem. The first screw conveyor is designed as a heating conveyor; it is inclined upward at an angle in its transport direction, thereby assuring that contaminated liquid which is introduced through the loading hopper will be able to collect only in the area below the loading hopper in a low-level screw conveyor section.
As long as a certain ratio of admixture of moist and dry wastes is kept within an average range, the liquid level in the lower part of the heated screw conveyor remains below the permitted maximum mark. If, however, large amounts of waste with a very high liquid content are introduced into the treatment apparatus, it can happen that the liquid level may rise above the permitted maximum mark in this area. This is because wastes in a purely liquid phase cannot, for obvious reasons, be conveyed by screw conveyors.
In U.S. Pat. No. 5,759,491 a method for treating infected materials is disclosed, in which the material to be treated is fed through a collecting area to a transport system which extends through the treatment chamber. There the heating as well as sterilization of disinfection takes place. The treated sludge is removed at the discharge end. Liquid can be pumped from a collecting tank into the collecting area or taken from the latter and pumped into the collecting tank.
EP-A-0 672 426 shows an apparatus for the treatment of infected wastes. Disinfection liquid is fed to the initially shredded wastes in a liquefaction station. This liquid is processed through a dewatering station adjoining a granulating and disinfecting station. The return of the disinfection liquid is thereby achieved.
Finally, DE 41 38 939 shows an apparatus and a method for the sterilization and disinfection of contaminated hospital waste. The granulated waste is thereafter fed to a disinfection screw conveyor and dried. Then follows a treatment with saturated steam and another drying.
The invention, therefore, is addressed to the problem of making available a method whereby even large amounts of purely liquid wastes produced in a short time can be safely treated independently of the treatment section actually designed for solid waste material in a high-temperature disinfecting apparatus. The invention is furthermore addressed to the problem in the treatment of contaminated materials, especially infected materials, which have a liquid phase and a solid phase, of providing an apparatus which will enable even large amounts of rapidly produced, purely liquid wastes to be safely disinfected or sterilized.
The problem is solved with regard to the method by a treatment of a kind in which
when liquid which has collected in the defined collection area of the treatment chamber reaches a given maximum liquid level it is conveyed to a collecting tank,
when the liquid level in the treatment reaches a given minimum level, liquid from the collecting tank is returned to the treatment chamber
when the liquid level in the collecting tank reaches a given maximum, liquid is fed back from the collecting tank to the treatment chamber if the maximum liquid level has not been reached in the treatment chamber, and/or is treated in an additional high-temperature disinfecting unit for liquids only.
By discharging liquid from the defined collecting area of the treatment chamber to a collecting tank, it is brought about that the given maximum liquid level in the treatment chamber is not exceeded, and thus contaminated liquid cannot spread undesirably within the treatment chamber and endanger the treatment process. Since liquid is returned from the collecting tank to the treatment chamber in case liquid is needed in the latter, it is brought about on the other hand that sufficient moisture is always available in the treatment chamber for producing the necessary vapor pressure. To prevent a given maximum liquid level in the collecting tank from being exceeded, liquid from this tank is selectively either returned to the treatment chamber as long as the maximum liquid level has not been reached therein, or it is treated in an additional high-temperature disinfection unit for liquid only.
Thus, even when contaminated materials having a high liquid content are to be treated, reliable disinfection or sterilization of the solid content of the material is always assured, since contaminated liquid cannot propagate uncontrolled in the treatment chamber. Since the liquid content of the material is fed to an additional high-temperature disinfection unit or sterilization unit, the treated liquid waste can be delivered directly into a sewer line, for example.
Preferably, provision is made in the method so that liquid from the collecting tank is returned to the treatment chamber only when the liquid level in the treatment chamber has reached a preset minimum level. This means that, if the liquid level in the collecting tank has reached the preset maximum level, as a rule liquid from the collecting tank is treated in the additional high-temperature disinfection or sterilization unit for liquids only.
The high-temperature disinfecting unit can be comprised substantially of a heat exchanger in which the liquid to be treated is heated at least to a certain temperature and this temperature is maintained for as long as is necessary for disinfection or for a sterilization.
The disinfection or sterilization by means of the heat exchanger can take place continuously if a permanent excess pressure is produced in the heat exchanger such that the stream of treated liquid leaving the heat exchanger is reduced by a throttling means such that when delivered by a pump a pressure builds up in the heat exchanger.
If a heat exchanger is provided as an additional high-temperature disinfecting unit and liquid is returned from the collecting tank into the treatment chamber only when the liquid level in the treatment chamber falls to a given minimumxe2x80x94that is, when a maximum is reached liquid from the collecting tank is otherwise transported away through the heat exchangerxe2x80x94provision is made preferably such that the collecting tank will be emptied through the heat exchanger only down to a predetermined average liquid level. In this way it is assured that sufficient fluid will always remain in the collecting tank to enable the liquid level in the treatment chamber to be raised when the minimum level is reached, without the addition of fresh water.
Also, it can be arranged according to the invention that the liquid can be disinfected or sterilized in the collecting tank, that is, the additional high-temperature disinfecting unit is the collecting tank itself, and that in this case more untreated liquid can be collected in a buffer tank which is disposed between the treatment chamber and the collecting tank. In this case the heat exchanger connected at the end can be omitted.
It can be arranged that the defined collecting area for liquid in the treatment chamber is created by tilting the treatment chamber upward in the direction of feed. In this case liquid introduced into the treatment chamber collects in a lower area of the treatment chamber that is established by the inclination. Also, the transport system is based on one or more screw conveyors.
The task of the invention is achieved with regard to the apparatus by an apparatus of this type which additionally has the feature that the collecting area of the treatment chamber is connected by at least one liquid line to a liquid collecting tank such that liquid can be carried out of the collecting area of the treatment chamber into the collecting tank and from the collecting tank back to the treatment chamber.
In this way, it is achieved that the liquid level in the collecting area of the treatment chamber can be varied very flexibly. Thus, when a maximum level has been reached, liquid can be carried out of the treatment chamber into the liquid collecting tank in order to reduce the amount of liquid in the treatment chamber. On the other hand, if the liquid level reaches a minimum level in the treatment chamber, liquid also can be returned from the collecting tank to the treatment chamber in order to assure that there is sufficient liquid in the latter to produce the necessary vapor pressure.
Preferably, it is arranged for the liquid collecting tank to be connected by a line to carry liquid to a high-temperature disinfecting or sterilizing unit provided in addition to the treatment chamber. Thus, it is accomplished that liquid can be carried out of the liquid collecting tank to empty it at any time, and this liquid can be disinfected or sterilized in the treatment chamber independently of the actual treatment process. The liquid that is treated can be discharged directly into a sewer line.
This additional high-temperature disinfection or sterilization unit can be based on a heat exchanger.
Alternatively, the liquid collecting tank itself can be designed as the additional high-temperature disinfection unit or sterilization unit. In this embodiment of the apparatus, a buffer tank can be provided between the treatment chamber and the liquid collecting tank for additional untreated liquid coming from the treatment unit. Liquid can be returned as needed from this buffer tank to the treatment chamber.
Both the liquid collecting tank and the buffer tank can be vented or can operate on the principle of an air chamber. While in the first case a pump is needed to carry liquid from the collecting tank, in the case of a liquid collecting tank operating on the air chamber principle, an elevated pressure can be built up by feeding liquid into it, so as to drive the liquid out of it when an outlet on the liquid collecting tank is opened. Also, in the case of a liquid collecting tank operating on the air chamber principle, a possibility can be provided for pumping air into the tank in order to facilitate a complete emptying of the liquid collecting tank. The same applies correspondingly to the buffer tank.
Preferably, the treatment chamber is oriented upwardly so as to produce the defined collecting area for liquid in the treatment chamber. Also, it is preferable for the transport system to have one or more screw conveyors which extend into the treatment chamber.